Using transplantable line Ib leukemia in syngeneic C58 mice, we have developed a computer model that accurately simulates the T cell mediated cellular immune response to malignant lymphoid cells. A manuscript summarizing this work has been accepted for publication in "Immunology," subject to editorial changes. Separate studies have analyzed the accuracy of the use of 51Cr and 125I labeled target cells for tumor cell lysis. These results are being summarized for publication along with a separate manuscript dealing with a computer based analysis of such findings. In a parallel study the effect of thymectomy and splenectomy on the immune response to tumor cells and on tumor cell kill has been analyzed. These results, along with a computer based analysis of the findings, are being prepared for publication.